Yes, I agree that the standard should conform the IEEE 754 standard for
floating-point computations that include infinities and NaNs. This is crucial for many applications that computes over floating-point values as the existence of symbolic values allows the interpreter/compiler taking care of overflows and exceptions.

Note that the sicstus mode is no more available in the last version of SICStus (4.0). As a consequence, floating-point variable cannot be unified to +inf, -inf or NaN. According to the SICStus Prolog developpers, this is due to their will to conform the ISO standard. They seems to be ready to get back to a mode where symbolic values would be available.

I had a look at floating point related issues again, in the context of thesuggested new prolog flags, but i've also discussed infinity and nan.My proposal is at http://eclipse-clp.org/Specs/core_float_20091008.txt(i tried to attach it, but the forum software doesn't allow .txt extensions...)